1. Field of Invention
The present invention relates to a jet-cleaning device for a CLEAN TRACK MK-V developing station. More particularly, the present invention relates to a jet-cleaning device having a vertical nozzle for establishing a vertical water jet so that waste liquid on a wafer back can be removed.
2. Description of Related Art
The manufacturing flow of integrated circuits (ICs) is rather complicated and involves hundreds of different processes requiring more than a month to finish. In general, the IC industry is a high-tech business that can be divided roughly into four main branches including IC design, wafer fabrication, wafer testing and wafer packaging.
Amongst the many steps required to fabricate semiconductor devices, photolithography can be regarded as one of the most frequently used processes. Any structures related to the fabrication of a MOS transistor, for example, patterning of various thin films or definition of doping areas, must be accomplished by a photolithographic process. Principally, a photolithographic process is carried out in three main steps including photoresist coating, light exposure and photoresist development.
In photoresist development, portions of the photoresist layer that have been illuminated by light are neutralized by chemicals and then removed so that a mask pattern hidden in the photoresist layer is revealed. In general, there are a number of ways for carrying out the development. However, in order to get photolithographic operations in-line with other processes, most manufacturers choose the "spray/puddle" method to develop photoresist. The spray/puddle method can be divided into three stages. In the first stage, developer is sprayed onto the surface of a wafer already placed on a spinner. Next, the developer is allowed to stay on the wafer surface for a period of time, in what is known as the puddle stage. Finally, after full development of the photoresist layer, the wafer is rinsed with water and then spun dry.
The aforementioned development processes can be accomplished on the same developing station. FIG. 1 is a cross-sectional side view showing a CLEAN TRACK MK-V developing station made by Japanese manufacturer.
The CLEAN TRACK MK-V developing station as shown in FIG. 1 is mainly used for developing 6 inch wafers. When the CLEAN TRACK MK-V developing station is carrying out a cleaning operation on wafer 14, the axle of spinner 10 provides a suitable vacuum so that the spin chuck 12 is able to grasp the wafer 14 by use of suction. As the spinner 10 spins, waste liquid on wafer surface 14 is carried to the edge and removed by centrifugal force. Through spinning, most of the waste liquid on the wafer surface is removed. However, some of the waste liquid will run onto the backside of the wafer 14. Hence, another cleaning operation to remove contaminants on the backside of the wafer 14 must subsequently be carried out.
FIG. 2A is a cross-sectional side view showing the jet-cleaning block of a conventional CLEAN TRACK MK-V developing station. FIG. 2B is a top view showing, the wafer back cleaning ring of a conventional CLEAN TRACK MK-V developing station.
On a conventional CLEAN TRACK MK-V developing station, contaminants on the backside of a wafer are removed through four jet-cleaning blocks 20 located above the wafer back cleaning ring, 18. The jet-cleaning blocks 20 are mounted onto the wafer back cleaning ring 18 through a set of fixed holes 28. Therefore, the jet-cleaning blocks 20 can be removed from the wafer back cleaning ring 18. Furthermore, there is a wall 16 acting as a barrier preventing the flow of waste liquid to the backside of the wafer. When the chemical solution or waste liquid try to flow onto the wafer back, the jet-cleaning block 20 on the wafer back cleaning ring 18 sends out a jet of water at an angle of about 45.degree.. The water jet is labeled 26 in FIG. 1. Water for the water jet 26, which removes the chemical solution and waste liquid, comes in through an Inlet 22 and out through an outlet 24. Details are shown in FIG. 2A.
The distance d.sub.1 from the edge of the wafer 14 to its center (for a 6-inch wafer) is 75 mm. The distance d.sub.2 from the center of the wafer 14 to the edge of the spin chuck 12 is 33 mm. If a wafer jet produced by a conventional jet-cleaning block 20 is used to clean to the wafer, only the area up to a distance d.sub.3 of about 25.5 mm from the edge of the wafer 14 can be reached. In fact, when chemical solution or waste liquid flows onto the wafer back, the back flow distance can be greater than d.sub.3. Therefore, a conventional jet-cleaning block 30 can at most clean the area covered by d.sub.3 while leaving contaminants behind in other areas.
In summary, the water jet formed by a conventional jet-cleaning block is roughly at a 45.degree. angle. Hence, the water jet is only capable of cleaning an area of about 25.5 mm from the edge of the wafer. Outside this area, this method is incapable of removing the waste liquid carried by a back flow.
In light of the foregoing, there is a need to design a better jet-cleaning block.